1. Field of the Invention:
The present invention relates to an electronic endoscope apparatus which employs a horizontal transfer clock of a fixed frequency with respect to the electronic scopes which incorporate solid state image elements each with a different number of pixels.
2. Description of the Related Art:
Recently, imaging apparatuses which employ a solid state imaging element such as a charge coupled device (hereinafter referred to as a CCD) as an imaging means have been widely used.
In the field of endoscopes, electronic endoscopes (hereinafter referred to as electronic scopes) which employ a CCD have been put into practical use and replaced the optical endoscopes (hereinafter referred to as fiberscopes) which employ an image guide for transferring an optical image.
The use of such electronic scopes have the advantage that the obtained image can be readily recorded or reproduced.
In the above-described electronic scopes, the size of an incorporated CCD determines the diameter of the portion of the electronic scope to be inserted, so CCDs having different sizes are used to enable cavities of different sizes to be observed.
These CCDs contain different numbers of pixels, depending on the type. However, the apparatus body to which the electronic scope is connected can only be used with an electronic scope incorporating one type of CCD with a particular specification, because the apparatus body incorporates a CCD drive circuit and a signal processing circuit which are designed to be used exclusively for that type of CCD.
Accordingly, the present assignee disclosed as a related technique in the specification of Japanese Patent Application No. 61-7472 an endoscope apparatus in which an oscillator and a tranfer pulse generating circuit are incorporated in each electronic scope so as to enable the remaining part of the apparatus body to be used with any scope. However, incorporation of an oscillator and other devices in each electronic scope increases the production cost and the size thereof.
The present assignee also disclosed an electronic endoscope apparatus in the specification of Japanese Patent Application No. 61-55512 in which a transfer pulse generating circuit is formed as one unit which is detachably mounted on the apparatus body. In this related technique, a drive pulse generating unit which corresponds to the employed scope must be combined to the apparatus body, making the operation complicated and increasing the possibility of erroneous operation if various types of scope are employed.